ANS and ENS Flashcards
Autonomic System
- The “self regulating” part of the nervous system controlling viscera, vasculature, glands
- Regulates homeostasis and reproduction
ANS can be largely influences by the CNS but also chemoreceptors, baroreceptors, mechanoreceptros to run automatically
Autonomic Afferent Systems Receptors
Mechanoreceptors
Chemoreceptors
Nociceptors
Thermoreceptors
Mechanoreceptors - ANS
Pressure
Baroreceptors in arteries (e.g. carotid sinus), lungs
Stretch
Veins, bladder, intestines
Chemoreceptors
- Carotid and aortic bodies (oxygen)
- Medulla (H, CO2)
- Hypothalamus (blood glucose, other electrolytes)
- Stomach/tongue/olfactory bulbs (various chemicals
Nociceptors
- Viscera and arterial walls
– Sensitive to stretch, ischemia, various irritating chemicals (e.g. inflammation)
Danger signs can be interpreted as pain
Thermoreceptors
Hypothalamus
* Blood temp
Cutaneous
* External temp
Information enters the CNS via:
- Spinal nerves through dorsal root to spinal cord
These then synapse with:
– Visceral efferents heading back out to organs (autonomic reflexes) Ex: Vomiting due to bad food
– Neurons ascending to brainstem, hypothalamus, thalamus
Visceral nociceptors also connect with:
– Somatosensory nociceptive afferents, contributing to referred pain
– Somatic efferents to skeletal muscle (muscle guarding); Goes back out to muscle tissue
— Ex: When sick you have tight muscles.
- Facial (VII), Glossopharyngeal (IX), Vagus (X)
– Info converges to solitary nucleus (in Medulla), the main visceral sensory nucleus
– From there, connections to:
— Pons and Medulla
— Hypothalamus, Thalamus, Limbic System
What does the Pons and Medulla do?
provide descending control to regulate HR, respiration, blood pressure, vasoconstriction/dilation
What does the hypothalamus, thalamus and limbic system do on the CNS?
Indirectly controls the Pons and Medulla
Visceral pain and referred pain
Visceral nociceptors may share the same dermatome or same transmitting neurons in the cord as somatosensory neurons
Constipation and Low Back Pain
- The two are often linked, confused, as constipation can cause muscle guarding
- Many pain medications make constipation worse – more muscle guarding – more back pain
- This can perpetuate a vicious cycle
How does the limbic system effect (psychological) effect the (physical) domain?
- Provides direct links between thoughts/beliefs, emotions, moods, and the overall state of the organism
- Part of the explanation for why stress kills people
- Or why how one feels about their job/spouse/life influences their pain experience
A ____ axon exits the central nervous system and synpases within a motor ganglion.
Basis of both sympathetic and parasympathetic nervous system pathways
myelinated
A ____ axon then exits this ganglion and travels to the target
Basis of both sympathetic and parasympathetic nervous system pathways
non-myelinated
Sympathetic Pathway: Origin and Pathway
- Originates: Hypothalamus
- Then goes through complicated multineuron pathway down to the intermediate column of the spinal cord between T1 and L2 Spinal Levels.
- Peripheral nerve exits the column through mixed spinal nerve to ventral ramus
- From ventral ramus enters the sympathetic trunk via white communicates
- Then travels up, down or out according to destination.
Pupillary Consensual Response vs Direct Pupillary Response
Direct Pupillary Response: A bright light shown into one eye will stimulate the parasympathetic response of pupillary constriction
Consensual Pupillary Reponse: Other eye constricts
This is due to the information coming back to the optic chiasm and splitting both ways. Signal goes to parasympathetic oculomotor nucleus on each side. Sends signal out to both eyes to constrict.
